Color tube beam indexing with ultra-violet rays



J. D. BOWKER 3,164,744

COLOR TUBE BEAM INDEXING WITH ULTRA-VIOLET RAYS Jan. 5, 1965 2 Sheets-Sheet 1 Filed May 23, 1961 AV/vI/Vi/ Jan. 5, 1965 J. D. BOWKER 3,164,744

COLOR TUBE BEAM INDEXING WITH ULTRA-VIOLET RAYS Filed May 23, 1961 2 Sheets-Sheet 2 INVENTOR. Jb/w/ ,0, Bow/(i2 United States Patent 3,164,744 CULQR TUBE BEAM INDEXENG WHTH ULTRA-VIOLET RAYS John D. Bowlrer, Princeton Junction, N.J., assignor to Radio Corporation of America, a corporation of Delaware Fiied May 23, 1961, S31. N 111,949 7 Claims. (Cl. 315-19) This invention relates to improvements in color-kinescopes of the line-screen feedback or sensing variety in which the control signals instead of being derived from the color-phosphors per se (as they are in Zworykin U.S. Patent 2,415,059) are derived from some added signalgenerating substance, such as an ultra-violet emitting phosphor (e.g., P16).

In the sensing ty e kinescopes of the prior art the signal-generating substance is either (a) mixed with or superimposed upon one of the color-emitting phosphors of each triad, or (b) contained in discrete strips or lines laid down either (i) between the color-phosphor'lines, or (ii) on the target surface of an electron-transparent specular metal layer that covers the rear surface of the light-emitting mosiac of color-phosphors.

In all sensing type screens of the prior art the pattern of the line-like signal-generating screen-areas bears some systematic relationship, for example, 1:1, 1:3 or 2:5, to the pattern of the screenis color-emitting phosphor triads. The requirement of precise register of these two patterns renders such screens difficult and extensive to make. This is so especially when, as is usually the case, the mosaic of color-phosphors has a specular metal backing which is opaque to the actinic rays employed in the photographic process by which said patterns are formed. Also, in present-day sensing type screens, special shapes or shading in the thickness of the signal-emitting areas are diflicult to achieve. Furthermore, because the signalemitting lines or strips are spaced from each other, some of the beam-electrons are periodically intercepted by the strips. Accordingly, unless the spaces between the signalemitting strips are provided, at additional expense, with a filling of an inert material, the color-pictures may contain an optically disturbing repetitive pattern of light and shade.

The foregoing and other less apparent disadvantages of color-kinescopes of the subject variety are minimized, in accordance with the present invention, by the following novel combination of elements:

(i) An electron-sensitive signal-generating screen comprising a line-like mosaic of color-phosphors having a signal-generating substance coextensively associated therewith, either in the form of a discrete layer or mixed with all of the color-phosphors of which the mosaic is comprised.

(ii) An optical stencil mounted remote from the path of the beam-electrons, yet exposed to the rays from the signal-generating substance; said stencil containing transparent and opaque areas arranged in a pattern which is systematically related to the pattern of the color-phosphor lines on the screen.

(iii) A phototube for converting the rays, passed by the stencil, into electrical signals indicative of the instantaneous position of the electron-beam on the screen.

The invention is described in greater detail in connection with the accompanying two sheets of drawings, wherein:

FIG. 1 is a schematic view of a portion of a television receiving system employing a color-kinescope having a 3-layer screen and showing an electro-optical arrangement including an optical stencil, lens and phototube for deriving beam-control signals from said screen, all in accordance with the principle of the invention;

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FIG. 2 is a rear view of the color-kinescope of FIG. 1 set up on a chassis and including an alternative type of electro-optical system for deriving control signals from the screen of said kinescope; and

FIGS. 3 and 4 are partly broken-away views in perspective of alternative screen structures which may be used in the practice of the invention.

The color-kinescope shown in FIG. 1 comprises an evacuated glass envelope 1 having a main chamber 3 which terminates at one end in a face-plate 5 and, at its opposite end, in a neck portion 7 in which the cathode 9, grid 11 and first anode 13 of a conventional electrongun are mounted. As is also conventional, a magnetic yoke 15 is provided on the neck of the tube for imparting the requisite horizontal and vertical scanning movements to the electron-beam from the gun. inner surface of the face-plate 5 which lies within the path of scan of the beam comprises the foundation surface of the electron-sensitive screen of the invention.

The substrate of this El-layer screen comprises a mosaic of red (R), blue (B) and green (G) phosphor lines, which are here arranged in a vertically extending repetitive pattern. The intermediate layer of this 3-1ayer laminate comprises an electron-transparent layer 17 of aluminum or other specular metal, and the third layer 19, which is the target surface of the screen, comprises an electrontransparent layer constituted essentially of a material (e.g., zinc oxide) which emits (ultra-violet) invisible actinic rays in response to the impact of the beam-electrons thereon. Both the intermediate layer 17 and the target layer 19 are coextensive with the entire scanned surface of the underlying color-phosphor mosaic RBG.

As above indicated, the electron-beam in scanning the light-emitting color-phosphor mosaic RBG passes through the target layer 19 and releases a corresponding beam or stream of invisible rays therefrom. This beam of invis ible rays, not shown, is reflected rearwardly by the specular metal layer 17 and passes through a window-like area 21 in the cone of the envelope. A first lens 23 impresses this moving beam of invisible rays upon an optical stencil 25 (later described). Another lens 27, which may be a Fresnel lens, impresses the now modulated beam of invisible rays upon a transducer, exemplified by a phototube 29, which converts said rays into electrical signals indicative of the instantaneous position of the beam on the mosaic.

Ordinarily the output of the transducer 29 is applied through an appropriate signal processing circuit 31 which, in combination with the incoming color video signals E E 13,. controls the instantaneous intensity of the beam. For an example of such circuitry, reference may be had to US. Patent 2,545,325 to Paul K. Weimer, issued March 13, 1951.

For the signal output of the phototube 29 to be representative of the instantaneous position of the electronbeam, the pattern of the transparent and opaque areas of the optical stencil 25 must bear some systematic relationship to the pattern of the light-emissive line-like mosaic pattern of the color-phosphors R, B and G. Such systematic relationship need not necessarily be the 1:1 relationship suggested by the sensing type screen of US. Patent 2,633,547, issued March 31, 1953, to Harold B Law. On that screen there is one signal-generating screen-area for each group of three (R, B and G) colorphosphor lines. With certain circuits a 1:3 or 2:5 relationship, for example, may be used to advantage. Similarly, the boundaries of the transparent and opaque areas of the optical stencil 25 neednot be sharp, nor do they need to be straight, but may comprise, for example, sinusoidal areas of light and shade.

The fact that the pattern of the optical stencil 25 bears That part of the 3 a systematic relationship to the pattern (REG) of the color-phosphor mosaic makes it possible to use the stencil to control the phase of the electrical signals derived from the phototube, and thus to control the hue of the colorpictures sketched on the mosaic by the electron-beam. Such phase and hue control is achieved by so mounting the optical stencil 25 that it may be moved laterally, as by a Vernier control mechanism 25s into and slightly out of register with the pattern (REG) of the color-phosphors.

If the pattern of the optical stencil Z5 is to exhibit the above-described 1:1 relationship with respect to the groups of phosphor lines (R, B, G) said stencil may comprise a photographically produced negative or positive replica, on a reduced scale, of the mask or screen (not shown) employed in the so-called direct photographic method of laying down the line-like mosaic of colorphosphors on the screen-plate 5. if another relationship (e.g., 1:3 or 2:5) is required, appropriate ones of the transparent areas of the photograph may be rendered opaque. If the indexing circuit, which includes the phototube 2?, is to provide electrical pulses of somewhat rounded or graded wave-shape, rather than sharp cor ners at top and bottom, such an effect can be provided by defocusing the optical system associated with the stencil either (a) during the manufacture of the stencil or (b) during the operation of the lainescope and its associated indexing circuit. Rounded or graded pulses avoid harmonics in the sensing circuits.

The invention is not limited in its practical applications to the particular form and arrangement of parts shown in FIG. 1. For example, in the embodiment of the invention shown in FiG. 2, the optical stencil, which is here designated 45, is curved instead of flat, and is supported upon the similarly curved window of the signal pick-up tube 49. The optical stencil may be either curved or fiat because its performance is related only to the relative position of the pattern of the optical stencil with respect to the pattern of color-phosphor lines on the screen of the kinescope. This phototube 49 (it may be a photomultiplier) as here shown, is mounted upon the same chassis 51 as the kinescope 1 and other tubes 53 and circuit components 55 of the set, thus simplifying its wiring, etc. Here the optical stencil 45 and the phototube 49 upon which the stencil is supported are out of a direct line with the port, or window 2i, through which the signal emanations emerge from the ltinescope. Accordingly, an optical system, exemplified by a lens 57 and a mirror 59 serves to transmit the signal emanations from the kinescope 1 to the remotely disposed pickup tube 49 upon which the optical stencil 45 is supported. The collecting lens 57 may be an integral part of the bulb l, or it may be mounted on the flare of the bulb with a suitable cement. If desired, the mirror 59 may be curved appropriately to provide a true catadioptric system.

In the colcr-lrinescope shown in FIG. 1, the signalgenerating ultra-violet phosphor 19 covers the rear or target surface of the specular metal layer 17. However, if the specular metal is made at least transparent to ultra-violet rays, then the P16 phosphor from which said rays emanate may be placed beneath the specular metal either by mixing it with the color-phosphors, as indicated by the legend in FIG. 3, or by laying it down in the form of film 19 on the rear surface of the mosaic REG, as shown in PEG. 4. The specular metal may be given the desired degree of transparency by crazing it, as indicated by the thread-like cracks c in the metal layer of FIG. 3, or by forming a sutficient number of holes h (FIG. 4) therein. One way of forming a crazed metal layer is to evaporate the metal onto a previously crazed organic substrate, e.g., a water based emulsion of a copolymer of an alkyl methacrylate and methacrylic acid dried to its solid state at a temperature lower than its film-forming temperature. Upon vaporizing the substrate the metal settles onto the mosaic in the crazed pattern exhibited by the substrate before it was vaporized. When a perforate, instead of crazed, metal layer is desired, the metal may be evaporated onto a substrate containing 15-22% polyvinyl acetate resin emulsion solids dispersed in 4-8% polyvinyl alcohol (remainder: water to make Upon vaporizing the substrate, the polyvinyl acetate decomposes and blows the holes 12 (FIG. 5) in the metal.

What is claimed is:

1. In combination: an electron-gun, an electron-sensitive screen mounted in a position to be scanned by a beam of electrons from said gun, said screen comprising a mosaic of color-phosphors and, coeXtensively associated with said mosaic, a substance that emits rays in response to the impact of said electron-beam thereon; an optical stencil mounted out of the path of said beam in a position whereat said stencil is exposed to said rays, the areas of said stencil which are transparent to said rays being arranged in a pattern which is systematically related to the pattern of said mosaic, and a transducer mounted in a position to receive the rays that have passed through said transparent areas of said stencil, said transducer being operable to convert said passed rays into electrical signals indicative of the instantaneous position of said beam on said mosaic.

2. The invention as set forth in claim 1 and wherein circuit means are provided for applying said electrical signals to the grid of said electron-gun to control the intensity of said beam as a function of the instantaneous position of said beam on said mosaic.

3. in combination, an evacuated envelope containing an electron-gun, a line-like mosaic of color-phosphors mounted within said envelope in a position to be scanned by a beam of electrons from said gun, said mosaic having coextensiveiy associated therewith a substance that emits invisible rays in response to the impact of said electron-beam thereon and said envelope having a window substantially transparent to said invisible rays, and means disposed exteriorly of said envelope for deriving from said invisible rays signals indicative of the instantaneous position of said electron-beam on said color-phosphor mosaic, said means comprising an optical stencil having areas transparent to said invisible rays arranged in a pattern which is systematically related to the line-like pattern of said color-phosphor mosaic.

4. In combination, an evacuated envelope containing an electron-gun, a line-like mosaic of color-phosphors mounted within said envelope in a position to be scanned by a beam of electrons from said gun, said mosaic having coextcnsively associated therewith a substance that emits invisible rays in response to the impact of said electronbeam thereon and said envelope having a window substantially transparent to said invisible rays, and means disposed exteriorly of said envelope for deriving from said invisible rays signals indicative of the instantaneous position of said electron-beam on said color-phosphor mosaic, said means comprising an optical stencil having areas transparent to said invisible rays arranged in a pattern which is systematically related to the line-like pattern of said color-phosphor mosaic, lens means for impressing said invisible rays on said stencil, and a transducer for converting the invisible rays which have passed through said optical stencil into electrical energy.

5. in combination, an evacuated envelope containing an electron-gun, a line-like mosaic of color-phosphors mounted within said envelope in a position to be scanned by a beam of electrons from said gun, said mosaic having coextensively associated in area therewith a phosphor that emits ultra-violet rays in response to the impact of said electron beam thereon, and optical stencil means disposed to receive rays from said phosphor that emits ultra-violet rays, said stencil having some portions transparent to said ultraviolet rays and other portions opaque to said ultra-violet rays, said portions being arranged in a pattern systematically related to said mosaic.

6. The combination of a cathode ray tube including a line-like mosaic of color-phosphors, a layer of ultra-violet emitting phosphor superimposed on said mosaic and coextensive in area therewith, and optical stencil means disposed adjacent to said layer so that ultra-violet emission from said layer is directed upon said stencil, said stencil having areas which are transparent to ultra-violet rays and which are arranged in a pattern that is systematically related to the line-like pattern of said mosaic.

7. The combination including a cathode ray tube and comprising an electron sensitive screen having a mosaic layer of line-like deposits of different-color-emitting phosphors, a specular layer of metal, and a layer of an ultraviolet emitting phosphor, said layers being superimposed in the order named and coextensive in area with each 15 3,013,113

other, electron gun means for projecting an electron beam onto said screen, and an optical stencil disposed in r the path of ultra-violet rays emitted from said ultra-violet References Cited in the file of this patent UNITED STATES PATENTS 2,604,534 Graham July 22, 1952 2,633,547 Law Mar. 31, 1953 2,923,846 Partin Feb. 2, 1960 Sunstein Dec. 12, 1961 

5. IN COMBINATION, AN EVACUATED ENVELOPE CONTAINING AN ELECTRON-GUN, A LINE-LIKE MOSAIC OF COLOR-PHOSPHORS MOUNTED WITHIN SAID ENVELOPE IN A POSITION TO BE SCANNED BY A BEAM OF ELECTRONS FROM SAID GUN, SAID MOSAIC HAVING COEXTENSIVELY ASSOCIATED IN AREA THEREWITH A PHOSPHOR THAT EMITS ULTRA-VIOLET RAYS IN RESPONSE TO THE IMPACT OF SAID ELECTRON BEAM THEREON, AND OPTICAL STENCIL MEANS 